Light controllable electrical switch

ABSTRACT

An electrical switch which can be remotely controlled to an &#39;&#39;&#39;&#39;ON&#39;&#39;&#39;&#39; or &#39;&#39;&#39;&#39;OFF&#39;&#39;&#39;&#39; state by the use of light energy radiations, but which can also be controlled at the switch location, if desired. The conditioning of the switch is controlled by means of a bistable electromechanical relay and by a pair of silicon controlled rectifiers.

United States Patent 1191 Long et al.

[ Aug. 13, 1974 LIGHT CONTROLLABLE ELECTRICAL SWITCH [73] Assignee: Princeton Electro Dynamics, Inc.,

Princeton Junction, NJ.

[22] Filed: Aug. 22, 1973 [21] Appl. No.: 390,532

[52] US. Cl 250/209, ZOO/61.02, 317/127 [51] Int. Cl. H0lh 47/24 [58] Field of Search 250/209; 317/127; ZOO/61.02

[56] References Cited UNlTED STATES PATENTS 3,767,924 10/1973 Charles et al 250/209 UTILIZATION ClRCUlT I OTHER PUBLICATIONS Anonev et al., A Photo-Control System for Air Blast Circuit Breakers, Elect. Technol. USSR 1969, V4, pp. 109117.

Primary Examiner.lames W. Lawrence Assistant Examiner-T. N. Grigsby Attorney, Agent, or FirmCharles l. Brodsky 5 7] ABSTRACT An electrical switch which can be remotely controlled to an ON or OFF state by the use of light energy radiations, but which can also be controlled at the switch location, if desired. The conditioning of the switch is controlled by means of a bistable electromechanical relay and by a pair of silicon controlled rectifiers.

6 Claims, 3 Drawing Figures PAIENTEnmm m4 3.829.683

CIRCUST CIRCUIT 1 LIGHT CONTROLLABLE ELECTRICAL SWITCH FIELD OF THE INVENTION This invention relates to electrical make and break switches, in general, and to such switches which can be remotely conditioned to an ON or OFF state for office buildings, schools, and manufacturing facilities where computer control of light switches, for example, is employed as a means to reduce costs of electricity.

SUMMARY OFTI-IE INVENTION As will become clear hereinafter, the constructions of the present invention are similar to those described in US. Pat. application Ser. No. 237,646, now U.S. Pat. No. 3,767,924, assigned to the same assignee as is this invention, in their use of light energy radiations'to provide local and remote controls in energizing and deenergizing electrical'devices. As with the constructions there described, the embodiments of this invention are designed to interface with computer, low voltage systems, so that the switches of the invention can be connected to the computer control center by low voltage, low current carrying conductors.

The arrangements described below are thus also especially attractive for use where the switches are employed in the control of lighting in office buildings, schools, and manufacturing plants, for example. Computer control signals could be coupled, as with the configurations of the US. Pat. Ser. No. 237,646 application, to turn of all lights in a particular part of the facility automatically after the work day has ended. Correspondingly, control signals can be sent to those switches at the beginning of the work day, to automatically turn all lights on. In those installations where personnel periodically make security checks, the computer can transmit control signals to turn the lights 'on just before the guard makes his rounds, and to turn them off" after they are completed. Conversely, all lights in a different part of a facility can be controlled to their temporary ON condition at the end of a work day, to be later turned off by a person working in that area at that time. Similarly, the computer control signal can be such as to place all lights in their temporary OFF mode just before the work day begins, to be individually turned on by the employees as they appear for work.

As will be seen below, the electrical make and break switches in accordance with the invention employ a bistable electromechanical relay and a pair of silicon controlled rectifiers, through which both local and remote control of the switch function can be regulated. Methods of optical multiplexing with light sensitive photocells and described to control the conductive state of the rectifier devices. Different from the constructions of the US. Pat. No. 3,767,924 case is the ultimate control of the make and break conditions of the switch being by means of the bistable electromechanical relay, rather than by solid state circuitry of the aforenoted patent. Added protection is afforded to the person servicing the switch with this electromechanical configuration in that the possible effects of leakage current will be less severe. That is, theleakage which could be expected under worst case conditions with the bistable electromechanical configuration will generally be insufficient to operate the relay in closing an electrical circuit path, whereas the leakage present in the solid state constructions of the reference patent application are imparted directly to the person handling the switch as no intervening circuitry is there present.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features of the present invention will be more readily understood from a consideration of the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an embodiment of the invention showing the manner by which lightenergy radiations can control the make and break functions of an electrical switch;

FIG. 2 is a schematic diagram of a second embodiment of the invention showing the manner by which optical multiplexing is employed to control the switch functions both from a local and from a remote location; and

FIG. 3 is a schematic diagram of a third embodiment of the invention showing the manner by which the control of the make and break functions is set at the remote location, regardless of the control sought to be exerted by a local user.

DETAILED DESCRIPTION OF THE DRAWINGS In FIG. 1, three terminals 10, 12, and 14 are shown. Terminal 10 serves as a ground or reference terminal while terminal 12 serves to supply the operating voltage for the system. Such voltage as is supplied between terminals l0, 12 may be of the order of volts alternating line voltage, but in a specific embodiment of the invention was of 277 volts rms magnitude as that represents the lateral voltage which is oftentimes employed in large office buildings in order to save copper costs. The primary winding 16a of a transformer 16 is coupled between terminals 10 and 12, while a pair of secondary windings 16b, 16c are serially coupled to step this 277 volts down to an amplitude suitable for powering the circuits of the construction. A semiconductor 18 has its anode electrode connected to the common junction of the windings 16b and 16c, and cooperates with as electrolytic capacitor 20, coupled between its cathode electrode and a point of ground potential, to develop a unidirectional voltage for energizing a pair of control lamps 22, 24. The turns ratios of transformer 16 are so selected that approximately 12 volts of alternating power is developed accross each secondary winding. As shown, the terminal of the transformer winding which is remote from the winding 16b is connected to the ground potential point.

A pair of silicon controlled rectifiers 26, 28 and a bistable electromechanical relay 30 are also shown. As indicated, one power electrode 26a of rectifier 26 is connected to one end a of a relay coil 32 in the bistable unit 30, while a second power electrode 26b of rectifier 26 is coupled to the reference potential point. In corresponding manner, one power electrode 28a of rectifier 28 is coupled to one end b of a second relay coil 34 in the bistable unit 30 while a second power electrode 28b of rectifier 28 is coupled to the ground point. The opposite end of the relay coil 34 and the opposite end of the relay coil 32 are joined together c, to which point is coupled the terminal of the transformer winding 16b which is remote from the winding 16c. As will be understood, current flowing through the relay coil 32 constitutes the make condition for the electrical switch, in which case a closed circuit path will exist between the supply terminal 12 and the third terminal of the drawing 14, between which terminals a utilization circuit 200 is connected. It will also be understood that current flowing through the relay coil 34 will break the switch connection, and open the circuit path between the terminals 12 and 14. The switch connection is particularly illustrated by the contact arm 202, joining points d and e of the relay 30 when closed.

The control lamps 22, 24 are each positioned adjacent a light sensing photocell the device 40 for the lamp 22 and the device 42 for the lamp 24-- so that light emitted from a lamp will only affect the conductivity of its adjacent photocell. One terminal of the photocell 40 is illustrated as being coupled to the end b of relay coil 34, while its other terminal is coupled to the junction between a pair of resistors 44, 46. Similarly, one terminal of the photocell 43 is coupled to the end a of relay coil 32, while its other terminal is coupled to the junction between a second pair of resistors 48, 50. Each of the resistors 46, 50 are returned to the ground potential terminal whereas the opposite ends of the resistors 44, 48 are coupled to the gate electrodes 26c and 28c of the silicon controlled rectifiers 26, 28 respectively. Lastly, a single pole double throw switch 60 is shown, which in the up most position of the drawing connects the remaining end of the lamp 24 to ground and in the lower most position, connects the remaining end of the lamp 22 to that reference potential point.

In operation and assuming the photocells to be constructed of cadmium sulphide material, moving the switch 60 downwards applies an energizing potential from the rectifier 18 and capacitor 20 to illuminate the lamp 22. The decrease in exhibited resistance by the photocell 40 permits the alternating voltage existent at terminal b of the relay coil 34 to be coupled to the gate electrode 260 of controlled rectifier 26 by means of the resistive divider 44, 46, to energize the silicon device 26. The resulting current flow through the relay coil 32 the current path comprising the two secondary windings 16b, 160, the relay coil 32 and the rectifier 26 energizes the electromechanical switch contact 202 to connect the load 200 between the terminals l2 and 14. With a GE RR7 type relay, only a momentary closure of the switch 60 is needed as the electromechanical relay 30 is bistable in its operation and will maintain contact arm 202 closed even though the switch 60 is then opened to turn off the lamp 22.

Defeat of this local, user control for closing the contact 202, on the other hand, follows the movement of the single pole double throw switch 60 to its upper most condition, to energize the control lamp 24. The alternating voltage then existent at terminal a of the relay coil 32 is applied through the lowered resistence photocell 42 to the gate electrode 28c of the silicon controlled rectifier 28 by the voltage divider 48, 50. This voltage renders the rectifier 28 conductive, again establishing a current path including the secondary windings 16b, 16c, but this time including the relay coil 34 and the rectifier 28. The flow of current through the coil 34 has the effect of open-circuiting the electromechanical switch contact 202, thereby disconnecting the load from the terminals 12, 14. As with the flow of current through the relay coil 32, a momentary flow of current through the coil 34 is all that is necessary to switch the bistable relay to its other condition, even though the momentary contact of the switch 60 to its upper most condition is thereafter broken to turn off the lamp 24.

In other words, alternatively adjusting the single pole, double throw switch 60 upwards and downwards, as shown in the drawings, not only illuminates the control lamp 24 and the control lamp 22, but also establishes the bistable type of switching action by means of which current flow removes and inserts the load 200 in circuit between the power and output terminals 12, 14. Resistors 46 and 50 are included to ensure that thermal leakage will not be sufficient to render either rectifier 26 or 28 conductive in the absence of their intended switching controls. In this manner, the load 200 will continue connected between the terminals 12 and 14 until the switch 60 is moved to energize the relay coil 34.

The modified embodiment of FIG. 2 first differs in its coupling of the photocells 40, 42 to the junction point c of the relay coils 32, 34, rather than to their end terminals, b of coil 34 and a of coil 32, respectively. The arrangement also differs in the selection of a different value for the resistors 44, 48, and in two other respects to be described below. First, the bistable electromechanical relay 30 is selected of a different GE type RR8 manufacture to provide a second contact arm control 204 when energized. To this end, a second semiconductor rectifier 62, a second electrolytic capacitor 64, a resistor 66 and a zener diode 68 are included. As shown, the anode electrode of the zener diode 68 and the negative plate of the electrolytic capacitor 64 are each connected to the ground potential point, with the positive plate of the capacitor 64 being connected directly to the cathode electrode of the diode 62, to which the cathode electrode of the zener diode 68 is coupled by means of the resistor 66. The anode electrode of the diode 62 is shown as coupled to point f of the contact arm control 204, its point 3 being referenced to the center tap 0" between the relay coils 32, 34. Whereas a current flow through the relay coil 32 in FIG. 1 energized the contact arm 202 to close, a current flow through the relay coil 34 in FIG. 2 additionally energizes the contact arm 204 to close.

Closure of the contact arm 204 in FIG. 2, however, serves to develop a direct current potential at the junction of resistor 66 with zener 68. This direct potential can be coupled to an auxiliary lamp circuit, to a reed switch, or to some other means of indicating that the state of the relay 30 is such that current flows through the coil 34. This auxiliary indicator could be coupled remote from the relay 30, for example at a computer control center, to indicate that the load 200 is then disconnected. This will be seen to follow as the contact arm 204 will be in its closed position only when the contact arm 202 is open, the disconnected condition of the load. This arrangement could be used to indicate, therefore, that all lights in a particular part of a building complex have been shut of The FIG. 2 embodiment secondly shows the inclusion of another pair of control lamps 70, 72, respectively adjacent the photocells 40, 42, to effect connection of the load 200 through a remote, instead of a local, user control signalling. Although not specifically shown, it will be understood that one terminal of the control lamps 70 and 72 will be connected to an energizing potential, while a signal pole, double throw switch of the type shown as 60 in FIG. 1 could be arranged to energize the lamp 70, for example, when it is desired-to turn on all lights in the building complex from a central computer or to energize'the lamp 72 to turn off all such lighting from the remote location. It should be noted that whichever of the lamps 70, 72 is illuminated by the remote switch, an opposite control effect could thereafter be accomplished by local energization of the lamps 24, 22, respectively. As with the illustrated configuration previously described, this single pole, double throw switch need operate only momentarily to ensure the correct state of the electromechanical switch.

The embodiment of FIG. 3 may be considered as being one for priority control, in that the switch condition can be regulated at a remote location, and therafter immunized from local user control. This construction includes a regulated power supply circuit 80 having a transistor 82 and zener diode 84 to develop an operating potential for the control lamps, photocells, and switching apparatus illustrated. The collector electrode of the transistor 82 is shown connected to the cathode electrode of the semi-conductor rectifier 18, while the base electrode of that transistor is coupled first, by a resistor 86 to that rectifier electrode and second, to the cathode electrode of the zener 84. The anode electrode of the zener diode 84 is connected to the reference groundpotential terminal, and a capacitor 88 is connected in parallel accross the zener element. In this instance, the component values and the turns ratios for the transformer 16 are selected so that a direct potential of substantially volts is developed at the emitter electrode of transistor 82. This potential serves as the energizing potential for the control lamps 22, 24 and, also, is shown as providing the energizing potential for the silicon controlled rectifiers 26, 28 by coupling to the photocells 40, 42.

Also shown in the drawing are four additional photocells 102, 104, 106, and 108 and two additional control lamps 110, 112. One terminal of each of the photocells 102, 104 is connected to receive the +10 volt energizing potential from the emitter electrode of transistor 82, while the other terminal of the photocell 102, 104 is coupled to the base electrode of an included transistor 114, 116, respectively. More particularly, the base electrode of transistor 114 is directly connected to the photocell 102, whereas the base electrode of transistor 116 is coupled to the photocell 104 by a capacitor 118. A first resistor 120 is coupled between the base and emitter electrodes of transistor 114 while a second resistor 122 is coupled between the base and emitter electrodes of transistor 116. As further shown, the emitter electrode of transistor 114 is connected to the ground potential terminal while the corresponding electrode of transistor 116 is connected to the junction of the resistors 44, 46. Lastly, the collector electrode of transistor 114 is directly connected to the gate electrode 26c of silicon controlled rectifier 26, the corresponding collector electrode of transistor 116 is connected to the 10 volt energizing potential, and a resistor 124 is included as referencing the capacitor 118 to ground. Comparable connections exist at the right half portion of FIG. 3, the portion associated with the silicon controlled rectifier 28, and corresponding components are identified by the same reference numeral, except higher by the number 30.

In considering the operation of the FIG. 3 construction, it will be appreciated that the control lamp 110 is physically positioned to illuminate only the photocells 102 and 108, while the control lamp l12'is positioned to illuminate only the photocells 104, 106. It will also be appreciated that these photocells are positioned so that no illumination from the control lamps 22, 24 will fall upon them. With this circuit, illuminating the control lamp 22 by moving the switch 60 downward couples a pluse of energizing current via photocell 40 and divider 44, 46 to the gate electrode 26c of the silicon controlled rectifier 26, thereby energizing the relay coil 32 and the contact arm 202 to connect the load 200 between terminals 12 and 14. This may constitute the temporary ON condition for the electrical switch. Illuminating the control lamp 24, on the other hand, by moving the single pole, double throw switch 60 upwards, provides a pulse of current via photocell 42 and divider 48, 50 to the gate electrode 280 of the silicon controlled device 28, to energize the relay coil 34 in disconnecting the contact arm 202 and the load 200 from between those terminals. This may constitute the temporary OFF condition for the electrical switch. The moving of the switch 60 to illuminate one or'the other of the two lamps 22, 24 may be under the control of a local user.

Assume that with the switch in its ON condition, the control lamp is then energized. The decrease in resistance of photocell 102 applies a positive potential from the +10 volt source to the base electrode of transistor 114, which when connected as shown in NPN fashion, clamps the gate electrode 26c of silicon rectifier 26 to ground. At the same time, the resistance of photocell 108 is decreased to apply a positive potential from the +10 source to the base electrode NPN transistor 146. This produces a pulse of current through .divider 48, 50 to the gate electrode 28c of rectifier28, to cause a current flow in relay coil 34. This switch in current flow from the relay coil 32 in the ON state to the relay coil 34 serves to disconnect the load 200 from between the terminals 12, 14, and place the switch in its OFF condition. The capacitor 148 and the resistor 152 comprise, in this respect, a delay circuit which, after the transistor 146 is rendered conductive, will build up a charge to turn that device non-conductive, thereby de-energizing the controlled rectifier 28 and its relay coil 34 current. The result will be, then, not only a switch in the bistable state of the electromechanical relay, but a further discontinuation of current flow in the relay so as to conserve power and extend the life of that electromechanical unit.

With the control lamp 110 then held in the illuminating condition, any attempt by the local user to illustrate his control lamp 22 to turn the switch back ON will be insufficient to cause current flow in the relay coil 32 because the current drive to the gate electrode 26c will be short circuited through the transistor 114 to ground. Holding the control lamp 110 to illuminating, therefore, with this construction, constitutes the permanent OFF condition for the light controllable switch. If the control lamp 1 10 were then turned off, local control of the lamp 22 could re-establish a current flow condition in the relay coil 32 to switch the load 200 back into circuit between the terminals 12, 14.

It will be seen from FIG. 3 that missing from the illustrated construction is the feedback arrangement of FIG. 2 by means of which an indication is received at the central computer location as to the condition of the remote switch. Without this indication, it is possible for the computer to direct that the electrical switch be turned to its OFF condition, but at a time when the switch is already in that state. Illuminating the lamp 110, however, serves only to clamp the transistor 114 to ground, and does not supply any current to the relay coil 32 in a direction to turn the switch ON. The current which is caused to flow through the relay coil 34 when the lamp 110 is illuminated has no deleterious effeet on the operation of the switch as the current flow through the relay coil 34 was already in the direction to turn the switch off.

Assume now that after the computer has permanently turned off the switch, i.e., has taken the load 200 out of the circuit, it becomes desirous to turn the switch back on. To accomplish this, for example by remote control at the central location, the lamp 110 is de-energized and the lamp 112 is illuminated. This lowers the resistance of the photocell 104, and causes a surge of current to be applied to the transistor 116 from the +10 volt source and from its emitter electrode, to the gate electrode 26c of the silicon rectifier 26 via divider 44, 46 to cause a current flow in the relay coil 32. This closes contact arm 202, and switches the load 200 back into circuit between the terminals 12 and 14, which condition continues to exist after the build up of charge on capacitor 118 causes transistor 116 to become nonconductive. At the same time, illuminating the control lamp 112 lowers the resistance of the photocell 106 to clamp the transistor 144 and when held illuminatingprevents any subsequent local user attempt at opening the switch by energizing lamp 24. In essence, this constitutes the permanent ON condition for the light controllable switch.

Thus, with both control lamps 110 and 112 inoperative, local control of an electrical switch can be effected through variations of the illumination of the control lamps 22, 24. Turning on the lamp 22 (even momentarily) causes a current flow in the relay coil 32 to turn the switch to its temporary ON condition. Turning the lamp 24 to its illuminating state (also momentarily) causes a current flow through the relay coil 34 to change the switch to its temporary OFF condition. Holding illuminated the lamp 110, however, places the switch in its permanent OFF condition and frees it from affect by user control of the control lamp 22. Conversely, holding illuminated the lamp 112 changes the switch to its permanent ON condition and frees the switch from any control by means of the lamp 24.

Such control operations will be apparent to one skilled in the art as being particularly desirable in controlling office lighting, as previously mentioned. Thus, at the end of the work day, remote control lamp 110 can be computer regulated to its illuminating condition, to permanently turn off all lighting in a specified portion of a facility. If security checks are then to be made, lamp 110 can then be turned off and lamp 112 can be turned on.All lighting will then be in an illuminating condition and can be turned off after the guard completes his rounds. On the other hand, at the beginning of the work day, the lamp 110 can be turned of and the lamp 24 turned on, so that workers can individually illuminate their work area as they come on the job, by turning on" their control lamps 22. At the of the work day, they can individually activate their control lamps 24 to turn off the lighting in their areas, prior to the computer being activated to illuminate lamp 110 to assure turn-off of all lighting. It will be readily understandable and appreciated that this manner of electricity control can serve to greatly lessen electricity costs in factories, office buildings, schools and the like.

While there have been described what are considered to be preferred embodiments of the present invention, it will be apparent to those skilled in the art that other bistable switch configurations can be devised without departing from the scope of the teachings herein of optically multiplexing both remote control and local control lamp sources in making and breaking electrical switch connections. It will also be apparent that in servicing these installations, an electrician will at times be called upon to replace the electromechanical relay unit 30.'Because these units are conventionally provided with air gaps in their construction and because the leakage currents associated with the silicon controlled rectifiers are generally not sufficient to traverse this air gap the electrician can feel free to handle these electromechanical relays without fear of electrical shock. In the constructions described in the US. Pat. No. 3,767,924, on the other hand, the end product control for the electrician to handle was the silicon controlled rectifier itself. In some instances and under certain conditions, the leakage current from the solid state device might present a shock hazard to the electrician. With the present constructions, Underwriters Laboratory approval and listing has been obtained, whereas approval for the solid state construction has yet to be granted.

It will similarly be appreciated that the feedback arrangement of FIG. 2 could be incorporated in the FIG. 3 construction to provide an outside indication of the particular stateof the electrical switch at any one time. Also apparent to those skilled in the art will be' the placing of the switch to its permanent ON condition by illuminating the lamp 112 in FIG. 3, assuming the switch to be initially off through local user control of lamp 24.

What is claimed is:

l. A controllable electrical switch comprising:

first and second terminals; and

actuating means for making electrical connection between said terminals when closing said switch and for breaking said electrical connection when opening said switch;

said actuating means including:

a. first and second sources of optical energy;

b. a bistable electromechanical relay having an input electrode coupled to said first terminal and an output electrode coupled to said second terminal and conditionable to one of a low and high impedance state between its input and output electrodes as a function of current flow therein;

as to place it in its low impedance state and such that a conductivity condition in the other of said devices produces a current flow in said relay as to place it in its high impedance state; and

d. regulator means for controlling the radiations of tween said terminals when closing said switch and optical energy from each of said first and second for breaking said electrical connection when opensources to change the conductivity condition of ing said switch; said semiconductor control devices as a function said actuating means including: of the radiations of optical energy from said a. first, second, third and fourth sources of optical sources with the imput circuits thereof, with said energy; change in conductivity condition serving to b. a bistable electromechanical relay having an change the current flow through the output circuit of said control devices to change the impeinput electrode coupled to said first terminal and an output electrode coupled to said second terdance state of said bistable relay in actuating said minal and conditionable to one of a low and high electrical switch from a make to a break condiimpedance state between its input and output tion and vice versa. electrodes as a function of current flow therein; 2. The controllable switch of claim 1 wherein the input circuits of each of said pair of semiconductor a pair of semiconductor control devices, each control devices includes an illumination detector for having an input circuit respectively responsive to determining which of said optical, sources is illuminatthe relative energy radiations from said first and ing at any one time in establishing the conductivity consecond optical sources and from said third and dition of said control devices. fourth energy sources and each having an output 3. The controllable switch of claim 2 wherein said ilcircuit respectively coupled to said electromelumination detector comprises a photocell exhibiting a chanical relay such that a conductivity condition resistance characteristic which varies inversely with the in one of said devices produces a current flow in amount of illumination impinging thereon. said relay as to place it in its low impedance state 4. The controllable switch of claim 3 wherein said and such that a conductivity condition in the bistable electromechanical relay includes a first relay other of said devices produces a current flow in coil responsive to current flow through the output cirsaid relay as to place it in its high impedance cuit of said one semiconductor control device to place state; and said relay in its low impedance state and a second relay d. regulator means for controlling the radiations of coil responsive to current flow through the output ciroptical energy from each of said first, second, cuit of said other semiconductor control device to third and fourth sources to change the conductivplace said relay in its high impedance state. ity conditions of said semiconductor control de- 5. The controllable switch of claim 4 wherein there vices as a function of the relative radiations of is also included means responsive to the current flow in optical energy from said sources with the input said second relay coil to provide an indication of the circuits thereof, with said change in conductivity impedance state of said bistable electromechanical condition serving to change the current flow relay and the conditioning of said electrical switch to through the output circuit of said control devices make and break electrical connections. to change the impedance state of said bistable 6. A controllable electrical switch comprising: relay in actuating said electrical switch from a first and second terminals; and make to a break condition and vice versa. actuating means for making electrical connection be- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No? 3,829,683 Dated Auq'ust 13, 1974 Inventofls) Donald C. long, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the abstract, at line 1 thereof, controlled should read -oonditioned-'-.-.

Colum 1, Line 31 I "u. s. Pat." should be deleted Coluxm 1 Line 57' "U.S. Pat." should read-Patent- Colurm 6, Line SO "the" (second occurrence) should read -thisculum a Line 51 "illustrate" should read-"inmate" Signed and sealed this 5th day ofNovember 1974.

(SEAL) Attest:

MCCQY Ma GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) uscoMM-oc eoa1 l=o9 353a 6I72 U. S. GOVIRNIINT FIIN ING OFFICE "OI 0-300-334 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,829,683 Dated August 13 1974 Inventofls) Donald C. Lonq, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below! In the abstract, at line 1 thereof, controlled should read --oonditioned-.-

Colum 1, Line 31 I "U. S. Pat." should be deleted Column 1, Line 57' "U.S. Pat." should mad -Patent" Column 6, 50 i "the" (second occurrence) should read --this Foluxm 6, line 5]. "illustrate" should read--il1uminate-- Signed and sealed this 5th day of'November 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Conunissione'r of Patents FORM Po-wso (10-69) uscoMM-oc eoavrpeo U.5, GOVIINHINT PIIIITING OFFICE "I! 0-lll-3Jl 

1. A controllable electrical switch comprising: first and second terminals; and actuating means for making electrical connection between said terminals when closing said switch and for breaking said electrical connection when opening said switch; said actuating means including: a. first and second sources of optical energy; b. a bistable electromechanical relay having an input electrode coupled to said first terminal and an output electrode coupled to said second terminal and conditionable to one of a low and high impedance state between its input and output electrodes as a function of current flow therein; c. a pair of semiconductor control devices, each having an input circuit respectively responsive to the energy radiations from said first and second optical sources and each having an output circuit respectively coupled to said electromechanical relay such that a conductivity condition in one of said devices produces a current flow in said relay as to place it in its low impedance state and such that a conductivity condition in the other of said devices produces a current flow in said relay as to place it in its high impedance state; and d. regulator means for controlling the radiations of optical energy from each of said first and second sources to change the conductivity condition of said semiconductor control devices as a function of the radiations of optical energy from said sources with the imput circuits thereof, with said change in conductivity condition serving to change the current flow through the output circuit of said control devices to change the impedance state of said bistable relay in actuating said electrical switch from a make to a break condition and vice versa.
 2. The controllable switch of claim 1 wherein the input circuits of each of said pair of semiconductor control devices includes an illumination detector for determining which of said optical sources is illuminating at any one time in establishing the conductivity condition of said control devices.
 3. The controllable switch of claim 2 wherein said illumination detector comprises a photocell exhibiting a resistance characteristic which varies inversely with the amount of illumination impinging thereon.
 4. The controllable switch of claim 3 wherein said bistable electromechanical relay includes a first relay coil responsive to current flow through the output circuit of said one semiconductor control device to place said relay in its low impedance state and a second relay coil responsive to current flow through the output circuit of said other semiconductor control device to place said relay in its high impedance state.
 5. The controllable switch of claim 4 wherein there is also included means responsive to the current flow in said second relay coil to provide an indication of the impedance state of said bistable electromechanical relay and the conditioning of said electrical switch to make and break electrical connections.
 6. A controllable electrical switch comprising: first and second terminals; and actuating means for making electrical connection between said terminals when closing said switch and for breaking said electrical connection when opening said switch; said actuating means including: a. first, second, third and fourth sources of optical energy; b. a bistable electromechanical relay having an input electrode coupled to said first terminal and an output electrode coupled to said second terminal and conditionable to One of a low and high impedance state between its input and output electrodes as a function of current flow therein; c. a pair of semiconductor control devices, each having an input circuit respectively responsive to the relative energy radiations from said first and second optical sources and from said third and fourth energy sources and each having an output circuit respectively coupled to said electromechanical relay such that a conductivity condition in one of said devices produces a current flow in said relay as to place it in its low impedance state and such that a conductivity condition in the other of said devices produces a current flow in said relay as to place it in its high impedance state; and d. regulator means for controlling the radiations of optical energy from each of said first, second, third and fourth sources to change the conductivity conditions of said semiconductor control devices as a function of the relative radiations of optical energy from said sources with the input circuits thereof, with said change in conductivity condition serving to change the current flow through the output circuit of said control devices to change the impedance state of said bistable relay in actuating said electrical switch from a make to a break condition and vice versa. 